Seatbelt device

ABSTRACT

Provided is a seatbelt device which prevents an occupant from hitting his face against an airbag deploying at the time of a vehicle collision. In order to take up any seatbelt slack before a collision and prevent the occupant from being displaced forward, the seatbelt device comprises a first tension modifier for winding the seatbelt and taking up the seatbelt slack when a collision is predicted, and a second tension modifier for further enhancing the tension of the seatbelt and securing the occupant to the seat at the time of such collision, thereby ensuring that the occupant does not exist in the airbag deployment zone when the airbag is activated.

This application is a division of application Ser. No. 09/657,359, filedSep. 7, 2000, and issued as U.S. Pat. No. 6,616,186.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a seatbelt device for securing anoccupant to a seat with a seatbelt and ensuring the safety of suchoccupant upon a vehicle collision.

2. Related Art

A known seatbelt device comprises a collision detector for detecting avehicle collision and outputting a collision signal, an airbag deployingin response to the collision signal, and a seatbelt device having apretensioner for retracting a seatbelt in response to the collisionsignal.

However, according to this invention, a large amount of the seatbelt isprotracted if, for example, an occupant is wearing clothes made of athick material. Consequently, the amount of the seatbelt that needs tobe wound would be large, because in order to effectively secure anoccupant with a seatbelt device having a pretensioner, the seatbelt musthave a tension above a prescribed value. If it takes time to effectivelysecure the occupant after an order for activating the pretensioner isgiven, the occupant is in the meantime displaced forward in thedirection of the collision, entering the zone where the airbag isdeploying. In other words, an occupant entering the airbag deploymentzone while the airbag is deploying may contact the airbag and hithis/her head against the inflating airbag at the speed of itsdeployment. Furthermore, winding of the seatbelt is delayed if thedetection of the vehicle collision is delayed, whereby the occupant isdisplaced in the direction of the collision. Here also, the occupant maybe displaced to the airbag deployment zone and hit his/her head againstthe airbag.

Furthermore, for the safety of the occupants it is preferred that anyvehicle employing a seatbelt device simply in combination with an airbaghas its seatbelt device exchanged to a seatbelt device comprising apretensioner. In such case, a traditional collision detector must alsobe exchanged to a collsion detector capable of driving both an airbagdevice and a pretensioner, but this increases the number of parts whichneeds to be exchanged and is also costly.

SUMMARY OF THE INVENTION

A purpose of this invention is to provide a seatbelt device preventingthe existence of the occupant's body in the airbag deployment zone.

Another purpose of this invention is to provide a seatbelt devicepreventing the existence of the occupant's body in the airbag deploymentzone, easily replaced with a seatbelt device of a vehicle alreadyequipped with an airbag device.

In order to accomplish the aforementioned purpose, a seatbelt deviceaccording to the present invention comprises; a seatbelt fasteningdetector for detecting that a tongue plate, through which a seatbelt forsecuring an occupant to a seat passes, has been engaged with a buckle; acollision predictor for predicting a collision of a vehicle andoutputting a prediction signal before the collision; a collisiondetector for detecting the collision of the vehicle and outputting acollision detection signal; an airbag device deploying in response tothe output of the collision detection signal; a first tension modifierand a second tension modifier capable of changing the tension of theseatbelt; and a controller for activating the first tension modifier inresponse to the prediction signal and enhancing the tension of theseatbelt, and activating the second tension modifier in response to thecollision detection signal and further enhancing the tension of theseatbelt.

With such structure, if, for example, an occupant is wearing clothesmade of a thick material, the first tension modifier is capable ofwinding before a vehicle collision any additional slack in the seatbeltcaused by the thickness of the material, which needs to be wound by asecond pretensioner serving as the second tension modifier. Therefore, alow-explosive powder pretensioner may complete the winding of theseatbelt before an inertia force displacing the occupant forward acts onthe seatbelt. Thus, the occupant is prevented from being displaced inthe direction of the collision further than a permitted range, and wouldnot hit his/her head, etc. against a deploying airbag.

Furthermore, a seatbelt device according to the present inventioncomprises: a seatbelt fastening detector for detecting that a tongueplate, through which a seatbelt for securing an occupant to a seatpasses, has been engaged with a buckle; a collision predictor forpredicting a collision of a vehicle and outputting a prediction signalbefore the collision; a collision detector for detecting the collisionof the vehicle and outputting a collision detection signal; an airbagdevice deploying in response to the output of the collision detection;an airbag activation detector for detecting the activation of the airbagdevice and outputting an airbag activation signal; a first tensionmodifier and a second tension modifier capable of changing the tensionof the seatbelt; and a controller for activating the first tensionmodifier in response to the prediction signal and enhancing the tensionof the seatbelt, and activating the second tension modifier in responseto the collision detection signal and further enhancing the tension ofthe seatbelt.

With such structure, if a vehicle already equipped with an airbag devicebut its seatbelt device does not include a pretensioner has its seatbeltexchanged to a seatbelt device having a pretensioner, the traditionalcollision detector need not be exchanged to a collision detector capableof driving both the airbag and the pretensioner. Exchanging atraditional seatbelt device to a seatbelt device having a pretensioneris relatively easy, and can be done at a low cost.

Preferably, the first tension modifier is a device for winding orprotracting the seatbelt by a motor power source, and the second tensionmodifier is a device for instantly retracting the seatbelt by a powersource of powder combustion gas.

Preferably, the airbag activation detector outputs the airbag activationsignal when a current supplied to an igniter for operating the airbagexceeds a prescribed current value, or when the temperature of theigniter exceeds a prescribed value.

Preferably, the airbag activation detector outputs the airbag activationsignal when any one of currents supplied to a plurality of igniters foroperating a plurality of airbags exceeds a prescribed current value, orwhen any one of the temperatures of the plurality of igniters exceeds aprescribed value.

Preferably, a seatbelt has a seatbelt retractor fixed to either avehicle body or the seat for winding the seatbelt, and the first tensionmodifier and the second tension modifier are provided to the seatbeltretractor.

Preferably, a seatbelt device has a seatbelt retractor which is fixed toeither a vehicle body or the seat for winding the seatbelt, and thefirst tension modifier is provided to the seatbelt retractor, and thesecond tension modifier is provided to the buckle portion.

Preferably, a seatbelt device has a seatbelt retractor which is fixed toeither a vehicle body or the seat for winding the seatbelt, and thefirst tension modifier is provided to the buckle portion and the secondtension modifier is provided to the seatbelt retractor, and the seatbeltretractor has a seatbelt locking mechanism for locking the protractionof the seatbelt when the first tension modifier is activated.

Preferably, the first tension modifier is provided to the seatbeltretractor winding one end of the seatbelt, and the second tensionmodifier is provided to the wrap belt fixing portion fixing the otherend of the seatbelt to a vehicle body or the seat.

Preferably, the second tension modifier is provided to the seatbeltretractor winding one end of the seatbelt, the seatbelt retractor has aseatbelt locking mechanism for locking the protraction of the seatbeltwhen the first tension modifier is activated, and the first tensionmodifier is provided to the wrap belt fixing portion fixing the otherend of the seatbelt to a vehicle body or the seat.

Preferably, the first tension modifier is provided to the buckleportion, and the second tension modifier is provided to a wrap beltfixing portion fixing the other end of the seatbelt to a vehicle body orthe seat.

Preferably, the first tension modifier is provided to the wrap beltfixing portion fixing the other end of the seatbelt to a vehicle body orthe seat, the second tension modifier is provided to a buckle portion,and the seatbelt retractor fixed to the vehicle body or the seat forwinding the seatbelt has a seatbelt locking mechanism for locking theprotraction of the seatbelt in response to an ordering signal.

Preferably, the first tension modifier and the second tension modifierare provided to a wrap belt fixing portion fixing the other end of theseatbelt to a vehicle body or the seat, and the seatbelt retractor fixedto the vehicle body or the seat for winding the seatbelt has a seatbeltlocking mechanism for locking the protraction of the seatbelt inresponse to an ordering signal.

Preferably, the seatbelt retractor is provided to the seat. The wrapbelt fixing portion is preferably provided to the seat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagram explaining the structure of the seatbelt device;

FIG. 2 is a diagram explaining an example of the structure of anelectric seatbelt retractor;

FIG. 3 is a diagram explaining a potentiometer 111;

FIG. 4 is a functional block diagram explaining the structure of acontroller 200;

FIG. 5 is a circuit diagram explaining an example of a structure of amotor driving circuit;

FIG. 6 is a flowchart explaining an example of controlling a firsttension modifier by a controller;

FIG. 7 is a flowchart explaining an example of controlling a secondtension modifier by the controller;

FIG. 8 is a flowchart explaining an example of controlling an airbagdevice by the controller;

FIG. 9 is a flowchart explaining the compulsory locking operation of aseatbelt locking mechanism controlled by the controller;

FIG. 10 is a graph showing changes in the seatbelt tension when theseatbelt device is activated;

FIG. 11 is a block diagram showing another example of a structure of thecontroller;

FIG. 12 is a flowchart explaining an example where the detection of avehicle collision by the controller is detected by the activation of theairbag device;

FIG. 13 is a perspective view explaining an example of a portion of aseatbelt retractor;

FIG. 14 is a perspective view explaining another example of a portion ofa seatbelt retractor;

FIG. 15 is a cross section of the locking mechanism of FIG. 14, shown inthe direction of the rotational axis of a ratchet wheel 18;

FIG. 16 is a diagram explaining the operation of a locking mechanismupon a rapid seatbelt protraction (seatbelt acceleration);

FIG. 17 is a diagram explaining a lock arm 26;

FIG. 18 is a diagram explaining an inertia plate 30;

FIG. 19 is a diagram explaining the operation of a locking mechanism bythe seatbelt acceleration;

FIG. 20 is a diagram explaining the operation of a locking mechanism bythe seatbelt acceleration;

FIG. 21 is a diagram explaining the operation of a locking mechanism bythe seatbelt acceleration;

FIG. 22 is a diagram explaining the operation of an electromagneticactuator (under an unlocked state);

FIG. 23 is a diagram explaining the operation of an electromagneticactuator (under a locked state);

FIG. 24 is a diagram explaining another example of an electromagneticactuator;

FIG. 25 is a diagram explaining an example where an electric winchserving as a seatbelt tension modifier is fixed to the buckle side;

FIG. 26 is a diagram explaining an example where an electric winchserving as a seatbelt tension modifier fixed to the seatbelt end;

FIG. 27 is a diagram explaining an example of a seat provided with aseatbelt retractor;

FIG. 28 is a diagram explaining a case where a pretentioner is providedon the buckle side; and

FIG. 29 is a diagram explaining a case where a pretentioner is providedat the seatbelt end.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, the embodiments of the present invention is explained below withreference to the relevant drawings.

FIG. 1 shows an example of a seatbelt device provided in a vehicle. Theseatbelt device is chiefly structured of: an electric retractor 100 forwinding a seatbelt 302 which is used for securing an occupant to a seat301; a through anchor 303 for folding back the seatbelt 302 in thevicinity of the occupant's shoulder; a tongue plate 305 engaged with abuckle 304 provided at the hip of the occupant, through which theseatbelt passes; an anchor 306 provided at the buckle, fixing an end ofthe seatbelt 302 to the vehicle; a switch 307 for detecting thefastening of the seatbelt, built in the buckle; a controller 200 (notshown) for controlling a seatbelt retractor 100; a collision predictor401 (not shown) for predicting a vehicle collision; and a collisiondetector 402 (not shown). Furthermore, an airbag device 500 is providedat the center portion of the steering wheel. Furthermore, other airbags(not shown) are also provided in the dashboard of the passenger seat andby the doors of the vehicle.

FIG. 2 is a diagram roughly explaining the structure of the seatbeltretractor 100. In this Figure, the seatbelt retractor 100 comprises aframe 101. Rotatably provided to the frame 101 are a reel 103 forwinding the seatbelt 302, and a reel shaft 103 a coupled with the reel103, which serves as an axis upon the rotation of the reel. Provided atthe right end of the reel shaft 103 a is a seatbelt locking mechanism102 (explained below) for locking the protraction of the seatbelt 302.The seatbelt locking mechanism 102 comprises: a VSI locking mechanismfor locking the protraction of the seatbelt when a prescribeddeceleration of the vehicle acts on the vehicle; and a WSI lockingmechanism for locking the protraction of the seatbelt when the seatbelt302 is protracted by a prescribed acceleration of the vehicle. Moreover,the seatbelt locking mechanism 102 is further provided with aelectromagnetic actuator 112 for performing a compulsory operation ofthe seatbelt locking mechanism 102 in response to an ordering signal.The operation of the electromagnetic actuator 112 is controlled by theoutput of the controller 200 explained below. The seatbelt lockingmechanism 102 is structured such that an electric motor 110 serving as afirst tension modifier may protract the seatbelt 302 even if the windingof the seatbelt 302 is “locked.”

A pretensioner 104 constituting a second tension modifier is actuated bythe output of the collision detector (not shown), and causes the reelshaft 103 a to rotate in the seatbelt winding direction and therebyperforms compulsory winding of the seatbelt in order to secure theoccupant to the seat. The pretensioner 104 may, for example, be a powderpretensioner, and be chiefly structured of a gas generator, a cylinderfor enclosing any gas generated from the gas generator, a piston movingwithin the cylinder by the pressure of the gas, and a transmissionmechanism for converting the movement of the piston to a rotationalmovement of the reel shaft 103 a via a crutch mechanism.

A pulley 105 secured to the reel shaft 103 a is connected to a pulley106 which is fixed to the axis of DC motor 110 via a power transmissionbelt 107. The pulleys 105 and 106 respectively have a prescribed numberof outer teeth formed along the outer peripheries thereof, and seatbelt107 has a prescribed number of inner teeth formed on the inner peripherythereof. The teeth of the pulley 105 used for the reel shaft and thepulley 106 used for the motor exactly match and mutually bite, and therotation of the motor 110 is thereby communicated to the reel shaft 103a. The motor 110 is secured at two points or more and is operated by theoutput of the controller 200.

As shown in FIG. 3, the potentiometer 111 provided at the leftmost endof the reel shaft 103 a is chiefly structured of a resister havingvoltage applied to both of its ends, and a slider which moves togetherwith the rotation of the reel shaft 103 a. Furthermore, a voltage valuecorresponding to the amount of the rotation from the standard positionof the reel shaft 103 a is output to the controller 200. Thus, theamount of seatbelt protraction, etc. can be estimated. Furthermore, bycomparing the voltage under the non-slack state of the seatbelt withthat under the protracted state of the seatbelt, the amount of the slackin the seatbelt can be estimated.

FIG. 4 is a functional block diagram explaining the schematic structureof the controller 200. As shown in FIG. 4, the controller 200 isstructured as a microcomputer system. A CPU 201 loads to the work areaof the RAM 203 the controlling program and the data held in ROM 202, andthereby controls the operation of the electromagnetic actuator (forexample, a solenoid) 112 which performs the compulsory operation of themotor 110 and the seatbelt locking mechanism 102.

The collision predictor 401 shown in FIG. 4 identifies whether or notthere is a possibility of a collision with a vehicle driving ahead orany other obstacles, and also whether or not such collision can beavoided. For example, a non-contacting distance sensor such as a laserradar, a supersonic sensor, etc. periodically measures the distancebetween another vehicle or an obstacle at predetermined moments. Arelative speed is calculated by the changes in such distance and theelapsed time. The time remaining until a collision is calculated bysubtracting the relevant distance according to the relative speed. Ifthe time remaining until the collision is shorter than the preset timeT1, the possibility of a collision is indicated by an output of acollision prediction signal. This signal is provided to an inputtinginterface 204, and a “collision prediction flag” in a flag region (flagregister) of a RAM 203 is thereby set “on.” As a consequence, theinterruption processing explained below is commenced by the CPU 201.

The output by a buckle switch 307 is communicated via the inputinterface 204, and a flag corresponding to the fastening/non-fasteningof the seatbelt is set in the flag region of the RAM 203.

The collision detector 402 detects by the acceleration sensor the impactcaused to the vehicle at the time of a collision, and processes anacceleration signal and detects a collision according to the size andthe initial waveform thereof. This signal is provided to the inputinterface 204, whereby a “collision detection flag” included in the flagregion of the RAM 203 is set “on.” As a consequence, the interruptionprocessing later explained is commenced by the CPU 201.

Furthermore, A/D conversions of voltages output by the aforementionedpotentiometer 111 is performed by the input interface 204 at prescribedintervals, but this processing has no direct relation with the presentinvention and is therefore not shown in the figure. The input interface204 internally comprises a CPU, and monitors the output voltage dataafter it has been converted. For example, if the value of the outputvoltage data obtained in the current processing differs from the outputvoltage data obtained in the previous processing, then the rotationalstatus of the shaft 103 a is identified, whereby either a “seatbeltprotraction” flag or a “seatbelt winding” flag is set to the flag regionof the RAM 203 depending on whether or not the difference in the outputvoltage is negative or positive compared with the data obtained in theprevious processing. Furthermore, the output voltage data is written tothe rotation amount area in the RAM 203 by a DMA operation. When theseatbelt has been wound, the change in the output voltage data in theseatbelt in the seatbelt protracting direction corresponds to the amountof the slack in the seatbelt. The amount of the slack in the seatbelt iswritten to the slack amount area in the RAM 203.

A current detector CT provided at a motor driving circuit 206 (explainedbelow) detects a voltage passing through the motor 110 as a voltagecorresponding to the current. The voltage is subject to A/D conversionsperformed by the input interface 204 at prescribed intervals, and isthereafter written to the motor current region in the RAM 203 by a DMAoperation. Since the current of the motor 110 is related with a torqueof the motor, the torque can be estimated by the value of the loadcurrent. The torque of the motor 110 constitutes a force (tension) forretracting the seatbelt 302.

When a prescribed condition set in the controlling program is fulfilled,the CPU 201 gives an output interface 205 a normal rotation order, areverse rotation order, or a drive suspension order regarding the motor110. The output interface 205 creates gate signals G1 and G2 pursuant tothese orders, and the signals are provided to the motor driving circuit206. When a normal rotation order is given, the gate signals G1 and G2are respectively set at “H” and “L”. When a reverse rotation order isgiven, the gate signals G1 and G2 are respectively set at “L” and “H”.When a drive suspension order is given, the gate signals G1 and G2 arerespectively set at “L” and “L”.

FIG. 5 is a circuit diagram showing an example of a structure of a motordriving circuit. A transistor bridge circuit is formed by fourtransistors, i.e., PNP transistors Q1 and Q2, and NPN transistors Q3 andQ4. Emitters of transistors Q1 and Q2 are mutually connected and a powersource Vc is supplied to their connection point. Furthermore, emittersof transistors Q3 and Q4 are mutually connected and the connection pointbecomes a ground level.

As already mentioned, the current detector CT detects the level of thecurrents outputted by the emitters for each of the transistors Q3 andQ4, and sends a level detection signal to the input interface 204. Theinput interface 204 performs an A/D conversion of the level detectionsignal, and thereafter writes the obtained data to the seatbelt tensionarea in the RAM 203 through a DMA operation. Since the value of the loadcurrent passing through the motor is related with the torque of themotor, the seatbelt tension F can be thereby estimated.

The collector of the transistor Q1 and the collector of the transistorQ3 are connected via a diode D1. The collectors of the transistor Q2 andQ4 are connected via a diode D2. The base of the transistor Q1 and thecollector of the transistor Q4 are connected via a bias resistance R1.The base of the transistor Q2 and the collector of the transistor Q3 areconnected via a bias resistance R2. A DC electric motor M is connectedbetween the respective collectors of the transistors Q1 and Q2.

With such structure, when a normal rotation order (G1=“H”; G2=“L”) issupplied to the respective gates of the transistors Q3 and Q4 from theoutput interface 205, the transistor Q3 becomes conductive and thetransistor Q4 becomes non-conductive. The collector of the transistor Q3becomes a ground level by the conductivity, and the base of thetransistor Q2 is biased to a low level (substantially a ground level)via the resistance R2 and makes the transistor Q2 conductive. Thecollector of the transistor Q4 becomes substantially the power source Vclevel, and the base of the transistor Q2 is biased to a high level viathe resistance R1 and makes the transistor Q1 non-conductive. As aresult, a current path is formed in a forward direction by a route:power source Vc, transistor Q2, motor M, diode D1, transistor Q3, andthe ground. Thus, the motor M rotates in the seatbelt winding direction.

When a reverse rotation order (G1=“L”; G2=“H”) is supplied to therespective gates of the transistors Q3 and Q4 from the output interface205, the transistor Q3 becomes non-conductive and the transistor Q4becomes conductive. The collector of the transistor Q4 becomes a groundlevel, and the base of the transistor Q1 is biased to a low level viathe resistance R1 and makes the transistor Q1 conductive. The collectorof the transistor Q3 becomes substantially the power source Vc level,and the base of the transistor Q2 is biased to a high level via theresistance R2 and makes the transistor Q2 non-conductive. As a result, acurrent path is formed in a reverse direction by a route: power sourceVc, transistor Q1, motor M, diode D2, transistor Q3, and the ground.Thus, the motor M rotates in a direction to protract the seatbelt.

When a drive suspension order (G1=“L”; G2=“L”) is supplied to therespective gates of the transistors Q3 and Q4 from the output interface205, both of the NPN transistors Q3 and Q4 become non-conductive. If thetransistor Q3 becomes non-conductive from a conductive state, thecollector of the transistor Q3 is enhanced from the ground level tosubstantially the power source level, and the base of the transistor Q2is biased to a high potential and the transistor Q2 is cut off.Similarly, if the transistor Q4 becomes non-conductive from a conductivestate, the collector of the transistor Q4 is enhanced from the groundlevel to substantially the power source level, and the base of thetransistor Q1 is biased to a high potential and the transistor Q1 is cutoff. Thus, if a drive suspension order is given, the respectivetransistors forming the bridge become non-conductive.

Returning to FIG. 4, upon fulfillment of a condition for operating thecompulsory lock of the seatbelt locking mechanism 102, the CPU 201 givesthe interface 205 a lock order signal (operation of the solenoid) Theactivation order signal set at the flag register of the output interface205 is amplified by a power amplifier 207 from a logic-level signal to alevel capable of activating the solenoid, and the signal is thenprovided to the solenoid 112. The operation of the solenoid causes thedisplacement of the actuator and the operation of the locking mechanism102 of the retractor 100. When operated, the seatbelt locking mechanism102 prevents the protraction of the wound seatbelt so that there is noslack in the seatbelt, but allows the winding of the seatbelt.

FIG. 6 is a flowchart explaining the control performed by a controller200. Here, the operation of a first tension modifier, namely, a seatbeltwinding motor is controlled.

By executing a main program, the CPU 201 periodically monitors theseatbelt fastening flag (S12). When the seatbelt fastening flag is “on”(S12; Yes), the CPU 12 determines the possibility of a collisionaccording to whether or not a collision prediction flag is set (S14). Ifthe flag is set (S14; Yes), the motor driving circuit 206 is operatedand the motor 110 serving as a slack remover or a tension modifier isdriven and made to rotate in the seatbelt winding direction for windinga webbing 302 (S16). Thus, the slack in the seatbelt is removed to acertain degree. For example, winding of the seatbelt may be performedeither until the tension of the seatbelt exceeds a prescribed value, orfor the duration of a prescribed period of time. The tension of theseatbelt can be identified by reading the sample value written in thecurrent value area in the RAM 203.

When the seatbelt is not fastened (S12; No) or the collision predictionflag is “off” (S14; No), there is no need to remove the slack in theseatbelt. Therefore, the CPU 201 orders the output interface 205 to stopdriving the motor 110, so that the motor would stop rotating to wind theseatbelt (S18). Consequently, the motor driving circuit 206 stopssupplying the motor 110 with a current, and the operation of the motor110 is terminated. The routine is thus terminated, and the processingreturns to the main program.

If a seatbelt is not fastened, the seatbelt is housed in the seatbeltwinding device 100 by the force of a seatbelt winding spring 114. Whenthe seatbelt is fastened, the minimum slack in the seatbelt is removed.

Now, referring to FIG. 7, the operation of the pretensioner serving asthe second tension modifier is explained.

The CPU 201 executes this routine either periodically or pursuant to aninterruption processing. If the seatbelt is fastened (S22; Yes), the CPU201 identifies whether or not any collision is detected (S24). If thecollision detection flag is set “on” and a collision is thereby detected(S24; Yes), the CPU 201 activates the pretensioner 104, which isactivated by an explosive system, as the second tension modifier. Theseatbelt is thereby quickly retracted, and the slack in the seatbelt istaken up, whereby the occupant is firmly secured. If the seatbelt is notfastened (S22; No), or no collision is detected (S24; No), the secondtension modifier is not operated, and the routine is terminated.

FIG. 8 is a flowchart explaining an example of controlling the operationof the airbag device.

The CPU 201 executes this routine either periodically or by aninterruption processing. If the collision detection flag is set “on” anda collision is thereby detected (S32; Yes), the CPU 201 supplies theairbag device with an ignition signal for igniting the low-explosivepowder, and the quick expansion of the combustion gas makes the airbagdeploy (S34). Thus, the occupant is saved from any secondary collisioninside the vehicle. If no collision is detected (S32; No), this routineis terminated.

FIG. 9 is a flowchart explaining the compulsory operation of theseatbelt locking mechanism.

If the first tension modifier operated by the collision detection signalfrom the collision detector 401 shown in FIG. 4 is, by itself, ortogether with the second tension modifier, operated by the collisiondetection signal which is output from the collision detector 402 shownin FIGS. 1 and 4 and communicated to a portion other than the seatbeltretractor (e.g., the securing portion of the buckle, or a wrap belt),then the operation of the tension modifier(s) acts in the direction forprotracting the seatbelt. Accordingly, the tension of the seatbelt isensured by performing a compulsory operation of the seatbelt lockingmechanism in advance and preventing any protraction of the seatbelt.

The CPU 201 executes the main program and periodically monitors theseatbelt fastening flag (S42). If the seatbelt fastening flag is “on”(S42; Yes), a possibility of a collision is detected depending onwhether or not the collision protection flag is set (S44). If the flagis “on” (S44; Yes), a lock ordering signal is communicated to the outputinterface 205, and the locking mechanism 102 of the retractor 100 isoperated. When operated, the seatbelt locking mechanism 102 prevents theprotraction of the wound seatbelt and the slack in the seatbelt, butallows the winding of the seatbelt (S46). The CPU 201 operates the motordriving circuit 206 and drives the motor 110 so that it rotates in theseatbelt winding direction for winding the webbing 302 (S48). Thus, theslack in the seatbelt is removed to a certain degree. For example,winding of the seatbelt may be performed either until the tension of theseatbelt exceeds a prescribed value, or for the duration of a prescribedperiod of time. The tension of the seatbelt can be identified by readingthe sample value written in the current value area in the RAM 203.

If the seatbelt is not fastened (S42; No), or the collision predictionflag is “off” (S44; No), the CPU 201 is not required to operate theseatbelt locking mechanism and a command for releasing the lock isprovided to the output interface 205. As a result, the lock is released,and the seatbelt can be protracted (S50). Subsequently, an order forceasing to drive the rotation of the motor 110 is provided to the outputinterface 205 (S52). Consequently, the motor driving circuit 206 stopssupplying the motor 110 with a current, and the operation of the motor110 is terminated. The routine is thus terminated, and the processingreturns to the main program.

Furthermore, if the seatbelt is not fastened, the seatbelt is stored inthe retractor 100 by the force of the winding coil 114. If the seatbeltis fastened, the minimum slack in the seatbelt is removed as explainedin the case above.

FIG. 10 is a graph which shows for the elapsed time the changes in theseatbelt tension when the first and second tension modifiers and theairbag device are activated by the controlling process illustrated inFIGS. 6 through 8.

In FIG. 10, the possibility of a collision is identified at time t1, andthe operation of the motor 110 is commenced and the tension of theseatbelt increases from F0 by the winding coil. At time t2, a collisiontakes place. At time t3, the collision is detected and the pretentioner104 and the airbag 500 are operated. Since the seatbelt is wound by themotor 110 and the pretensioner 104, the tension of the seatbelt quicklyrises from tension F1 as of t1. Due to the impact of the collision, theseatbelt locking mechanism 102 locks the protraction of the seatbelt bya VSI operation. After time t4, where the tension of the seatbeltreaches F2, the tension is further increased by the addition of aforward inertia force acting on the occupant in the direction toprotract the seatbelt from the retractor 100.

Furthermore, when the impact of the collision is added to the vehicle,the protraction of the seatbelt is locked by the VSI sensor located atthe seatbelt retractor 100. Moreover, if the seatbelt 302 is quicklyprotracted by the WSI sensor located at the seatbelt retractor 100, theprotraction of the seatbelt 302 is locked.

FIG. 11 is a block diagram explaining the second embodiment of thepresent invention. In this figure, components corresponding to those ofFIG. 4 are shown with the same reference numerals, and explanations forsuch components are omitted.

According to this example, an operation of the airbag 500 providedindependently from the seatbelt devise and operating independently fromthe seatbelt device is used by the seatbelt device for detecting acollision.

When a collision detection signal is communicated to the airbag device500 from the collision detector 402 detecting the collision of thevehicle, an ignition current is conducted through an ignition squib,whereby the low-explosive powder ignites and expansion gas is generated,and the airbag deploys. Supply of the ignition current is detected bythe activation detector 510. Regarding the detection of the ignitioncurrent, activation of the airbag, for example, can be detected bymounting a clamp-type current sensor on a wire harness through which theignition current flows, and determining whether or not the detectedcurrent exceeds a prescribed value. Otherwise, activation of the airbagmay be detected by providing a temperature sensor in the vicinity of theigniter of the airbag and identifying an activation of the airbag whenthe temperature of the ignited portion exceeds a prescribed value.

The activation detector 510 supplies the input interface 204 with anactivation detection signal. Through a DMA operation, the inputinterface 204 sets the activation detection flag “on” in the flag regionof the RAM 203. This means that a vehicle collision has taken place, andtherefore, the aforementioned collsion detection flag may be set “on”.

In some cases, multiple airbag devices 500 can be provided at the centerportion of the steering wheel, in the dashboard of the passenger seat,by the side doors, etc. In such cases, as shown in FIG. 11, anactivation detectors 510 can be mounted on each of the airbag devices,so that the activation detection signal in each of the activationdetector 510 is provided to the input interface 204. This allows the CPU201 to determine that a vehicle collision has taken place. Other partsof the invention have the same structure as explained above.

FIG. 12 is a flowchart explaining an example of controlling theoperation of the pretensioner constituting a second tension modifier,synchronizing with the operation of the airbag device.

The CPU 201 executes this routine either periodically or by aninterruption processing. If the seatbelt is fastened (S62; Yes), the CPU201 identifies whether or not activation of the airbag device isdetected (S64). If the activation detection flag is set “on” and theoperation of the airbag device, i.e., a collision is detected (S64;Yes), the CPU 201 operates the powder pretensioner 104 serving as thesecond tension modifier (S66). The seatbelt is thereby quickly wound,and the slack in the seatbelt is removed, whereby the occupant is firmlysecured. If the seatbelt is not fastened (S62; No) or no collision isdetected (S64; No), the second tension modifier is not activated, andthis routine is terminated.

FIGS. 13 through 24 are exploded perspective views of the retractor 100and longitudinal sectional views of the major part thereof, chieflyexplaining the seatbelt locking mechanism 102 (the mechanical lockingmechanism of the reel, the WSI locking mechanism which is operated whensensing the seatbelt protraction acceleration, the VSI locking mechanismwhich is operated when sensing the vehicle deceleration, etc.), and theelectromagnetic actuator 112. As shown in FIG. 9, when a possibility ofa collision is identified, a compulsory locking of the seatbelt lockingmechanism 102 takes place. Accordingly, the mechanical locking mechanismexplained below is provided mainly for securing the occupant at the timeof a collision if the operation of this compulsory lock is hindered forany reason. In an example shown in FIG. 13, no pretensioner is provided.If a pretensioer is required due to the property of the vehicle, thepretensioner 104 shown in FIG. 2 is provided between a retractor base 1and a power transmission unit 15 shown in FIG. 13.

In FIGS. 13 through 18, the major part of the retractor base has asubstantially U-shaped cross section. The facing side plates 1 a and 1 bhave facing winding shaft through holes provided thereon. The reel 3,which serves as the winding shaft for winding the seatbelt 302 (notshown), passes through these winding shaft through holes and isrotatably provided thereto.

The winding shaft through holes on the side plate 1 a has inner gearteeth 2 formed along its inner periphery, and a ring 4 is providedoutside of the winding shaft through hole. A drawing processing isperformed on the inner periphery of the ring 4, and when the ring 4 isfixed to the outside of the side plate 1 a by a rivet 40, a gap isformed in the axial direction between the inner gear teeth 2 and theinner periphery edge of the ring 4.

The retractor base 1 further comprises, on the side plate 1 a side, anemergency locking mechanism for preventing any protraction of theseatbelt upon an emergency. Furthermore, provided to the side plate 1 bside of the base 1 is a power transmission unit 15 which includes: apulley 105 connected to an axis 15 c (corresponds to the reel shaft 103a) driven by the electric motor 110 via a timing belt 107; a windingcoil 114; and a potentiometer 111 (all not shown). The reel 3 issubstantially a cylindrical winding shaft integrally formed of aluminumalloy or the like. A barrel 28 to which the seatbelt is wound has a slitopening 28 a in the diameter direction for passing and holding theseatbelt end therein. Furthermore, on the outer periphery of the reel 3,a flange 13 formed as a separate body is provided for preventing anywinding disorder of the seatbelt. Furthermore, the seatbelt is woundalong the outer periphery of the reel 3 mounted on the retractor base 1.The seatbelt is inserted and passed through the seatbelt guide 41 fixedto the upper portion of the back plate of the retractor base 1, and theincoming/out position of the seatbelt is thereby restricted.

A protruding rotation spindle for rotatably supporting the reel 3 isprovided to both ends of the reel 3. A separately-formed spindle pin 6is press fitted to the sensor side end face of the reel 3 and serves asa rotation spindle. The sensor side end face of the reel 3 furthercomprises a protruding spindle 7 which rockably supports a pole 16serving as a lock member engagable with the inner gear teeth 2 formed onthe side plate 1 a. Furthermore, when the pole 16 rocks and rotates inthe direction to engage with the inner gear teeth 2, the positions ofthe rocking side end of the pole 16 and the rear end 16 ethereof on theopposite side are defined, and when a large load is fastened to an areabetween the inner gear teeth 2 and the pole 16, a pressure receivingface 45 for receiving the load is provided on the sensor side end faceof the reel 3.

Furthermore, on the sensor side end face of the reel 3, a stopperprotrusion 8 is provided for the purpose of preventing acounterclockwise rotation of the rocking lever 20 supported in arockable manner by a ratchet wheel 18 which serves as a latch member ofthe lock operator explained below. A concave part 9 constitutes a recessfor preventing any interference to the reel 3 either by the extensioncoil spring 36 urging the rotation of the ratchet wheel 18 in theseatbelt protracting direction (direction of arrow x2 shown in FIG. 14)or by an arm portion 26 c of the lock arm 26 pressing the sensor spring25 explained below.

The rocking end of the pole 16 comprises an integrally-formed gear teeth16 c which corresponds to and is engagable with the inner gear teeth 2formed on the side plate 1 a. Moreover, a spindle hole 16 a, to which aspindle 7 is fitted with some recess, penetrates the center of the pole16. Furthermore, an engaging protrusion 16 b located on the rocking endside and an engaging protrusion 16 d located on the rear end 16 esideprotrude from the sensor side end face of the pole 16.

In other words, since the spindle 7 is loosely fitted to the spindlehole 16 a, the pole 16 is rockably and rotatably supported by thespindle 7, and is capable of making relative movements in a prescribedamount. Furthermore, the tip of the spindle 7 penetrating the spindlehole 16 a of the pole 16 is fastened by the stopper hole 17 b of aretaining plate 17, and a through hole 17 a of a retaining plate 17 ispenetrated by a spindle 6 which is press fit to the reel 3. Theretaining plate 17 prevents the pole 16 from lifting up from the endface of the reel 3.

Furthermore, the end of the engaging protrusion 16 b of the pole 16 isinserted into the cam hole 18 aof the ratchet wheel 18. The ratchetwheel 18 is located at the outside of the retaining plate 17 androtatably supported by the spindle pin 6. When the relative rotation ofthe ratchet wheel 18 with respect to the reel 3 is in the seatbeltwinding direction (direction of arrow X1 in FIG. 14), the cam hole 18 amoves the end of the engaging protrusion 16 b radially outward from therotation shaft of the reel 3. As a consequence, the pole 16 is made torock and rotate around the spindle 7 in the direction (direction ofarrow Y1 in FIG. 13) to engage with the inner gear teeth 2 formed on theside plate 1 a.

Namely, the pole 16 rocks and rotates in the direction to engage withthe inner gear teeth 2, and the engagement of the teeth 16 c of the pole16 with the inner gear teeth 2 constitutes a locking device forpreventing any rotation of the reel 3 in the seatbelt protractingdirection. The ratchet wheel 18 is a ratchet rotatably supported by thespindle pin 6. On the outer periphery of the ratchet wheel 18, ratchetteeth 18 b are provided for engagement with the sensor arm 53 of thevehicle acceleration sensor 51. Furthermore, a flange 6 a of the spindlepin 6 supports, as its axis, the center hole 30 a of the inertia plate30, i.e., a disc inertia element serving as a sensor for sensing theseatbelt protraction acceleration. In the vicinity of the center hole ofthe ratchet wheel 18, a stopper pawl portion 23 engages with theengaging hole 30 b and thereby determines the position of the inertiaplate 30 in the thrusting direction thereof. The long hole 24 formed onthe ratchet wheel 18 is engaged with the engaging protrusion 31 of theinertia plate 30, and an edge 24 a of the long hole 24 determines theposition of the rotating direction of the inertia plate 30 when theemergency locking mechanism is not operated (see FIG. 16).

As shown in FIG. 16, the outer side face of the ratchet wheel 18comprises, protruding therefrom, a shaft 22 which supports the lock arm26 as an axis and a spring hook portion 55. Furthermore, as shown inFIG. 20, the inertia plate 30 has an opening 56 through which the springhook portion 55 is inserted. The opening 56 is formed as a long holesuch that the inertia plate 50 is able to relatively rotate with respectto the ratchet wheel 18 while the spring hook 55 is inserted therein,and a spring hook portion 57 corresponding to the spring hook 55 isprovided at one end of the opening 56.

A compression coil spring 58 is fitted and inserted between a pair ofthe spring hooks 55 and 57. As shown in FIG. 19, the compression coilspring 58 is urged so that the engaging protrusion 31 on the inertiaplate 30 is maintained in an unlocked state where the inertia plate 30touches the other end 24 b of the long hole 24 formed on the ratchetwheel 18.

Provided on the inner side face of the ratchet wheel 18 is a spring hook21. The extension coil spring 36, the one end of which is hooked by thehook 17 c of the retaining plate 17, has its other end hooked by thecoil hook 21. The extension coil spring 36 urges the rotation of theratchet wheel 18 with respect to the reel 3 in the seatbelt protractingdirection (in the direction of arrow X2). As shown in FIG. 17, the lockarm 26 includes a stopper pawl 26 b capable of biting an inner teethgear 34 a of a gear case 34, and also an arm portion 26 c for pressingthe center portion of the linear sensor spring 25 in a longitudinaldirection, whose both ends are supported by a pair of hooks 18 d formedon the outer side face of the ratchet wheel 18.

Accordingly, the lock arm 26 bites the inner teeth gear 34 a, therebyengaging with the stopper pawl 26 b and constituting a stopper elementfor preventing the rotation of the ratchet wheel in the seatbeltprotracting direction. By the urging force of the sensor spring 25, thestopper pawl 26 b is pressed and urged toward the contacting portion 32of the inertia plate 30. Furthermore, the ratchet wheel 18 correspondingto the rocking range of the arm portion 26 c has an opening for thepenetration of the arm portion 26 c formed thereon, which is providedsolely for ensuring the engagement of the arm portion 26 c with thesensor spring 25.

As a cam face grinding and contacting the back 26 d of the stopper pawl26 b of the lock arm 26, the contacting portion 32 is structured of afirst cam face 32 a not affecting the lock arm 26 by the rotation of theinertia plate 30, and a second cam face 32 b for rocking the arm 26 incorrespondence with the delay in the rotation of the inertia plate 30from the rotation of the reel 3 and causing the stopper pawl 26 b tobite the inner teeth 34 a.

The emergency locking mechanism being unlocked, the first cam face 32 acontacts the back 26 d of the lock arm 26, and the back 26 d does notcontact the second cam face 32 b until the delay in the rotation of theinertia plate 30 from the rotation of the reel 3 exceeds a prescribedvalue. Regarding the length of the first cam face 32 a, i.e., thequantity of the rotation of the inertia 30 in the state of the back 26 dslidably contacting the first cam face 32 a, if the rotation of theinertia plate 30 is delayed from the rotation of the reel 3 by theinertia force acting on the inertia plate 30 when the entire seatbelt isretracted, the first cam face 32 a is set at a length to prevent theback 26 d of the lock arm from reaching the second cam face 32 b by suchlevel of delay in the rotation.

Furthermore, the lock arm 26 according to the present embodimentincludes a contacting pawl 26 eat its rocking end located opposite tothe stopper pawl 26 b. Corresponding to the contacting pawl 26 e, theinertia plate 30 includes a step 33 to which the contacting pawl 26 ecancontact. The step 33 is provided for enabling such contact of thecontacting pawl 26 ewhen the inertia plate 30 is at its initial positionunder an unlocked state, and thereby restricting the rotation andmovement of the lock arm 26 in the locking direction. As shown in FIGS.20 and 21, when the rotation of the inertia plate 30 is delayed morethan a prescribed value and the back 26 d of the lock arm 26 touches thesecond cam face 32 b, the lock arm 26 can rock in the looking directionby the pressing effect of the second cam face 32 b.

Furthermore, on the spindle 19 protruding from the inner side face ofthe ratchet wheel 18, a rocking lever 20 supported by an shaft hole 20 ais rockably provided. A counterclockwise rotation of the rocking lever20 is suitably restricted by the stopper protrusion 8 protruding fromthe sensor side end face of the reel 3. Furthermore, the rocking lever20 is assembled between the reel 3 and the ratchet wheel 18, so thatwhen the pressing protrusion 16 d protruding from the sensor side facecontacts an area between the spindle 19 and the stopper protrusion 8,the clockwise rotation of the rocking lever 20 is suitably restricted.

At the center portion of the gear case 34 provided outside the inertiaplate 30, a shaft support or 34 b is provided via the spindle 6 torotatably support the reel 3. A collar 6 a of the spindle 6 contacts thebottom face of the shaft supporter 34 b, which constitutes a surface fordefining the axial direction of the reel 3. Furthermore, provided at thelower portion of the gear case 34 is a box-shaped housing 50 whichhouses the vehicle acceleration sensor 51 for sensing the accelerationof the vehicle.

The sensor cover 35 is provided outside the side plate 1 a covering thegear case 34.

Next, the operation of the aforementioned seatbelt retractor isexplained below. Foremost, as shown in, FIG. 19, in a normal state, theratchet wheel 18 is urged with respect to the reel in the seatbeltprotracting direction by the urging force of the extension coil spring36 hanging from a hook 17 c of a plate 17, and the pole 16 having anengaging protrusion 16 b which engages with a cam hole 18 a is therebyurged in a direction to disengage from the inner gear teeth 2.Consequently, the reel 3 can rotate, and the seatbelt is freelyprotracted.

Thus, if the seatbelt acceleration sensor or the vehicle accelerationsensor 51 including the inertia plate 30 is activated upon an emergencysuch as a vehicle collision, a rotation of the ratchet wheel 18 in theseatbelt protracting direction is prevented either by the lock arm 26 orthe sensor arm 53 which serve as stopper elements for preventing therotation of the ratchet wheel 18 in the seatbelt protracting direction,and the locking element of the retractor is activated.

After the vehicle acceleration sensor 51 or the seatbelt accelerationsensor is activated and the seatbelt is protracted from the retractor,the rotation of the ratchet wheel 18 is delayed compared with therotation of the reel 3, and the ratchet wheel 18 performs a relativerotation in the seatbelt winding direction (direction of arrow X1).Thus, the cam hole 18 a of the ratchet wheel 18 displaces the engagingprotrusion 16 b on the pole 16 radially outward from the central axis ofrotation. The pole 16 thereby rockably rotates around the spindle 7 in adirection (direction of arrow Y1 in FIG. 13) to engage with the innergear teeth 2.

Furthermore, when the seatbelt is protracted from the retractor, thegear teeth 16 c bites the inner engaging 2 and the operation is therebycompleted. Under this condition, there is a gap between the rear end 16eof the pole 16 and the pressure receiving face 45 of the reel 3, whilethe rotation of the rocking lever 20 is restricted by both the stopperprotrusion 8 of the pole 3 and the pressing protrusion 16 d of the pole16 with almost no recess.

The spindle 7 of the reel 3 loosely fits into the spindle hole 16 a ofthe pole 16, such that the spindle hole 16 a is rockably and rotatablysupported, capable of making relative movements toward the reel 3 in aprescribed value. Therefore, if the seatbelt is protracted from theretractor, the pole 16 performs relative rotations with respect to thereel 3 around the rotational axis of the reel 3 until the rear end 16econtacts the pressure receiving face 45.

In such case, although the pressing protrusion 16 d of the pole 16 is inan immobile position with respect to the side plate 1 a, the stopperprotrusion 8 of the reel 3 rotates in the seatbelt protracting direction(direction of arrow X2). As a result of this movement, the rocking lever20 rockably rotates in the clockwise direction shown in FIG. 14 as therocking end is pressed by the stopper protrusion 8, and is made torockably rotate around the pressing protrusion 16 d being the fulcrum ofits rotation. When the rocking lever 20 rockably rotates in theclockwise direction in FIG. 14 around a contact point of the rockinglever 20 and the pressing protrusion 16 d, the shaft hole 20 a rotatablysupported by the spindle 19 of the ratchet wheel 18 rotates in theseatbelt winding direction (direction of arrow X1) with respect to thecentral rotational axis of the reel 3. As a result, the ratchet wheel 18rotates in the reverse direction with respect to the reel 3 in theseatbelt winding direction (in the direction of arrow X1).

Accordingly, even if the vehicle acceleration sensor 51 or the seatbeltacceleration sensor is activated and the locking element of theretractor is “locked” for preventing the rotation of the reel 3 in theseatbelt protracting direction, the ratchet wheel 18 which is preventedfrom rotating in the seatbelt protracting direction can be set “free” inorder to disengage from the inner gear teeth 34 a of the gear case 34either the sensor arm 53 of the car acceleration sensor 51 or the lockarm 26 of the seatbelt acceleration sensor.

When the pole 16 is locked, any larger tension acting on the seatbeltcauses deformation of the supporting axis 34 b of the gear case 34 andthe portion supporting the axis 15 c of the power transmission unit 15,and the reel 3 attempts to move upward. This can be avoided by thecontacting face 3 a and a groove 3 b formed on the reel respectivelycontacting the inner gear teeth 2 and the gear teeth 62 formed on theside board 1 b (see FIG. 13), and the tension acting on the seatbelt isreceived by these surfaces.

By the time the vehicle stops and the tension acting on the seatbelt isreleased, the engagement between the ratchet wheel 18 and the innerteeth gear 34 a formed on the gear case 34 of the sensor arm 53 or thelock arm 26 has been released, and the urging force of the extensioncoil spring 36 makes the ratchet wheel 18 rotate with respect to thereel 3 in the direction of arrow X2, such that the cam hole 18 a of theratchet wheel 18 displaces the engaging protrusion 16 b of the pole 16to the rotational axis side of the reel 3. At this time, the tensionacting on the seatbelt in the seatbelt protracting direction is releasedin the manner described above and the reel 3 is permitted to rotate inthe seatbelt winding direction (direction of arrow X1) Accordingly, ifthe reel 3 rotates in the direction of arrow X1 without the tip of thegear teeth 16 c of the pole 16 involving with the tip of the inner gearteeth 2, then the pole 16 rockably rotates around the spindle 7 in adirection to disengage from the inner gear teeth 2, and the reel 3 isthereby unlocked and the seatbelt can be freely protracted.

Subsequently, under the seatbelt protracting state, the electric motor110 winds the seatbelt, and if the full length of the seatbelt israpidly wound in accordance with the torque of the power transmissiondevice 15, the inertia plate 30 serving as an inertia element of theseatbelt acceleration sensor continues to rotate in the windingdirection with respect to the reel 3 which has suddenly stoppedrotating, such that the rotation of the inertia plate 30 proceeds in thewinding direction with respect to the reel 3 and the rotation of theinertia plate 30 is delayed in respect to the protracting direction ofthe reel 3. However, the contacting portion 32 of the inertia plate 30,which makes the stopper pawl 26 b of the lock arm 26 rock in a directionto engage with the inner gear teeth 34 a of the gear case 34, isstructured of two cam faces 32 a and 32 b for making the stopper pawl 26b rock toward the inner teeth gear 34 a only after the delay in therotation of the inertia plate 30 (in comparison with the rotation of thereel 3) has reached a prescribed values Therefore, the stopper pawl 26 bdoes not rock in a direction to engage with the inner teeth gear 34 auntil the delay in the rotation of the inertia plate 30 (in comparisonwith the rotation of the reel 3) has reached a prescribed value.

The embodiment of the present invention has a structure explained above.The activated locking mechanism is further provided with an electricmagnetic actuator 112 as shown in the lower part of FIG. 14. Thisactuator is required for the processing illustrated in FIG. 9 mentionedabove. As shown in FIGS. 22 and 23, the electric magnetic actuator 112is structured of a solenoid (excitation coil) 112 a, a coil spring(elastic element) 112 b, a collar plunger (magnetic core) 112 c, etc.and is provided at the lower part of the vehicle acceleration sensor 51.

In a normal state, the solenoid 112 a is excited. Under this condition,as shown in the Figures, the plunger 112 c does not contact a ballweight 54 and therefore does not affect the locking mechanism 51. When acontroller 200 releases the excitation of the solenoid 112 a in order tolock the seatbelt (S30, etc.), the plunger 112 c is raised by the urgingforce of the spring 112 b. Through an opening formed on the bottom faceof sensor cover 52, the tip of the plunger 112 c pushes up the ballweight 54. When the ball weight is lifted up, the sensor arm movesupward in FIG. 22 and the engaging protrusion 53 a engages with theratchet teeth 18 b of the ratchet wheel 18. Thus, the rotation of theratchet wheel in the seatbelt protracting direction (direction of arrowX2 in FIG. 14) is prevented. When the seatbelt is protracted and thereel 3 is rotated in the seatbelt protracting direction, due to thedifference in the rotation of the locked ratchet wheel 18 and therotation of the reel 3, the pole 16 is displaced radially outward andengages with the inner gear teeth 2 of the frame 1 a. The rotation ofthe reel 3 in the seatbelt protracting direction is thereby prevented.

According to this example, the locking operation is not conducted whenthe solenoid 112 a is supplied with an excitation current. The lockingoperation takes place when the excitation current is cut off. In otherwords, the locking mechanism can be activated by supplying low-levelactivation signals. Therefore, the seatbelt can be locked when the powersource of the seatbelt device is cut off.

FIG. 24 is a diagram showing another example of a structure of anelectromagnetic actuator 112. According to this example, theelectromagnetic actuator is structured of: the solenoid 112 a; theplunger 112 c; a lever 112 d substantially in L-shape, engaged with theplunger 112 c at one end and having its center portion rotatabalysupported; and a coil spring urging the lever 112 d in the clockwisedirection in FIG. 24. When the pawl of the lever 112 d is displaced andtouches a tooth face 18 b of the ratchet wheel 18, the rotation of theratchet wheel 18 is prevented and the locking mechanism is operated bythe pole 16 and the frame of the inner teeth 2.

In a normal state where the solenoid 112 a is supplied with anexcitation current from the controller 200, the solenoid 112 a resiststo the coil spring 112 b and draws the plunger 112 c, whereby the otherend of the pawl of the lever 112 d is separated from the ratchet wheel18. Accordingly, the locking mechanism is not activated.

Furthermore, in order to lock the seatbelt, the supply of the excitationcurrent from the controller 200 is cut (at S46, etc.) The coil spring112 b pulls out the plunger 112 c downward in the Figure by its urgingforce, thereby rotating the lever 112 d. As a consequence, the pawl atthe other end of the lever 112 d engages with the teeth 18 b of theratchet wheel 18 and the rotation of the ratchet wheel in the seatbeltprotracting direction is prevented. When the seatbelt is protracted andthe reel 3 rotates in the direction of the protraction, the differencein the rotations of the engaged ratchet wheel 18 and the reel 3displaces the pole 16 radially outward and the pole 16 engages with theinner teeth 2 formed on the frame 1 a. Thus, the rotation of the reel 3in the seatbelt protracting direction is prevented, and the locking iscompleted.

FIGS. 25 through 29 show examples of structures of other seatbeltdevices employing the present invention. In each drawing, componentscorresponding to those of FIG. 1 are shown with the same referencenumerals.

FIG. 25 shows another example of a seatbelt device employing the presentinvention. In this example, an electric winch 310 comprising a motor 311and a reel 312 for winding the wire 313 connected to the buckle 304 isprovided as a tension modifier for winding or protracting the seatbelton the buckle 304 side. The wire is protracted or wound by a normal or areverse rotation of the motor 311. Instead of driving the motor 110, thecontroller 200 drives the motor 311 of the winch 310 so that the slackin the seatbelt 302 is removed. Here also, the tension of the seatbeltcan be estimated by detecting the current value of the motor 311. Withthis structure, it is preferred that the seatbelt retractor 100 has acompulsory locking mechanism and a pretensioner, but the seatbeltretractor need not be electric. The anchor 306 for securing one end ofthe seatbelt 302 can be fixed to the seat 301. By doing so, theprotracted length of the seatbelt 302 is made shorter and the slack inthe seatbelt can be removed faster.

FIG. 26 shows an example of another seatbelt device employing thepresent invention. According to this example, the tension modifier forremoving any slack in the seatbelt is provided on the side of the anchor306 (wrap belt fixing portion) for securing one end of the seatbelt 302.Similar to the example above, a tension modifier may be structured of amotor 311 and an electric winch 310 having a reel 312 for winding thewire 313 connected to the buckle. As a possible variant, a tensionmodifier may be structured of a screw shaft which is rotated and drivenby the motor and the nut which performs reciprocating motion along thescrew shaft.

According to the example shown in FIG. 27, the seatbelt retractor 100 isfixed not to the bottom of the center pillar of the vehicle but to theseat 301. The present invention can also have such structure.

The example shown in FIG. 28 is structured of an electric retractor anda pretensioner 104 a provided on the buckle side.

The example shown in FIG. 29 is structured of an electric retractor anda pretensioner 104 b provided on the side of the anchor 306 for securingone end of the seatbelt 302.

Furthermore, a pretensioner can be incorporated in the electric winch310 shown in FIGS. 25 and 26.

Although the seatbelt device according to the above-described embodimenthas an electric motor as a first tension modifier and a powderpretensioner, which is activated by an explosive system, as a secondtension modifier, both tension modifiers may have electric motors.Furthermore, a spring may be used as a power source. Either or both ofthe first and second tension modifiers may be mounted on the seatbeltretractor, and either or both of the first and second tension modifiersmay be mounted on a component other than the seatbelt retractor. In suchcase, the tension modifier(s) may be mounted on the buckle side or onthe wrap belt securing portion side.

Furthermore, since the vehicle collision detector activating thepretensioner is operated when the output of the deployment (operation)of the airbag is detected, the cost of the device is further reduced.

As explained above, according to the seatbelt device of the presentinvention, the slack in the seatbelt is removed by the first tensionmodifier prior to a collision, and the occupant is secured to the seatby the second tension modifier at a higher tension concurrently with thedeployment of the airbag. Therefore, it is possible to save the occupantfrom being hit by the airbag.

1. A seatbelt device comnrising: a seatbelt fastening detector thatdetects that a tongue plate, through which a seatbelt for securing anoccupant to a seat passes, has been engaged with a buckle; a collisionpredictor that predicts a collision of a vehicle and outputs aprediction signal before said collision; a collision detector thatdetects said collision of the vehicle and outputs a collision detectionsignal; an airbag device that deploys in response to the output of saidcollision detection signal; an airbar activation detector that detectssaid activation of said airbag device and outputs an airbag activationsignal; a first tension modifier and a second tension modifier thatchange the tension of the seatbelt; and a controller that is programmedto activate the first tension modifier in response to said predictionsignal and to enhance said tension of the seatbelt, and to activate thesecond tension modifier in response to said airbag activation signal andfurther to enhance said tension of the seatbelt, wherein said airbagactivation detector outputs said airbag activation signal when a currentsupplied to an igniter for activating the airbag exceeds a prescribedcurrent value, or when the temperature of said igniter exceeds aprescribed value.
 2. A seatbelt device comprising: a seatbelt fasteningdetector that detects that a tongue plate, through which a seatbelt forsecuring an occupant to a seat passes, has been engaged with a buckle; acollision predictor that predicts a collision of a vehicle and outputs aprediction signal before said collision; a collision detector thatdetects said collision of the vehicle and outputs a collision detectionsignal; an airbag device that deploys in response to the output of saidcollision detection signal; an airbag activation detector that detectssaid activation of said airbag device and outputs an airbag activationsignal; a first tension modifier and a second tension modifier thatchange the tension of the seatbelt; and a controller that is programmedto activate the first tension modifier in response to said predictionsignal and to enhance said tension of the seatbelt, and to activate thesecond tension modifier in response to said airbag activation signal andfurther to enhance said tension of the seatbelt, wherein said airbagactivation detector outputs said airbag activation signal when any oneof the currents supplied to a plurality of igniters for activating aplurality of airbags exceeds a prescribed current value, or when any oneof the temperatures of said plurality of igniters exceeds a prescribedvalue.
 3. A seatbelt device comprising: means for detecting that atongue plate, through which a seatbelt for securing an occupant to aseat passes, has been engaged with a buckle; means for predicting acollision of a vehicle and outputting a prediction signal before saidcollision; means for detecting said collision of the vehicle andoutputting a collision detection signal; airbag device that deploys inresponse to the output of said collision detection signal; means fordetecting activation of said airbag device and outputting an airbagactivation signal; first tension modifying means and a second tensionmodifying means capable of changing the tension of the seatbelt; andcontrol means for activating the first tension modifier in response tosaid prediction signal and enhancing said tension of the seatbelt, andactivating the second tension modifier in response to said airbagactivation signal and further enhancing said tension of the seatbelt,wherein said means for detecting activation of said airbag deviceoutputs said airbag activation signal when a current supplied to anigniter for activating the airbag exceeds a prescribed current value, orwhen the temperature of said igniter exceeds a prescribed value.
 4. Aseatbelt device according to claim 3, wherein said means for detectingactivation of said airbag device outputs said airbag activation signalwhen any one of the currents supplied to a plurality of igniters foractivating a plurality of airbags exceeds a prescribed current value, orwhen any one of the temperatures of said plurality of igniters exceeds aprescribed value.